1. Field of the Invention
The invention relates to a recording method and drive for optical storage media, and more particularly to a recording method and drive for optical storage media, which are capable of positioning a starting position for succeeding the recording by searching for a special pattern recorded on an optical disk.
2. Description of the Related Art
A recordable compact disk (CD-Recordable or CD-R) or a rewritable compact disk (CD-Rewritable or CD-RW) is a CD-type optical disk medium, and includes a continuous spiral groove. Input data is modulated and recorded into the continuous spiral groove. The input data is composed of the main data, error correction data, address information, and other miscellaneous content. The channel modulation for CD-type medium is the eight-to-fourteen modulation (EFM). The eight-to-fourteen modulation modulates every eight-bit data symbol into one fourteen-bit codeword with three-bit merging bits. In the CD-type specifications, data is recorded in unit of sector, which is accessed at a constant linear velocity (CLV).
FIG. 1 illustrates the data architecture for each recording unit in a typical CD-RW optical disk. Referring to FIG. 1, each recording unit includes 75 sectors. Each sector includes 98 frames, each of which has 588 bits and is composed of a 24 bit sync pattern, 14 bit control and display data, information data, correction polarity data, and the like. The unit of each bit is T. The restricted records may be placed in the table of content (TOC) of the optical disk for positioning the starting point of the sector. Because a part of the data has been set and recorded in advance, it is important to prevent the drive recording process from being interrupted.
The typical CD-RW includes a buffer for buffering the input data in advance and indexing the input data to the corresponding sectors so that the data is recorded into the continuous area of the optical disk. However, when the buffer of the CD-RW cannot receive data from the host (e.g., the host is interrupted by the job having higher priority), the buffer will be empty owing to lack of data (data under-run), thereby causing the recording process to be interrupted and causing the recorded data hard to be retrieved.
In view of the problem, U.S. Pat. No. 6,119,201 discloses a data under-run protection method using formatted padding sectors. The method of this patent is to solve the problem of data under-run by recording one or more formatted padding sectors to prevent the recording process from being interrupted when the data under-run occurs. However, the method wastes some recordable area on padding the data of one or more formatted padding sectors. In addition, the reading time will be wasted to judge if the data is the padding sector during the reading process. Furthermore, the method cannot overcome the problem of recording interruption caused by an error of the control for the focus/tracking servo, or a shock to the drive.
Therefore, it is necessary to provide a drive and a method for directly succeeding the recording without additionally padding data when the recording process is interrupted due to data under-run or other reasons.
The frame length of the recorded data needs to be precisely controlled to a nominal length of 588T (bits) when retrieving the recorded data, so that the optical drive can correctly retrieves the recorded data. FIG. 2 illustrates a schematic diagram showing two overlapped frames when the recording is succeeded, wherein FIG. 2A illustrates the recording signal before interruption, the signal after the recording being succeeded, and the recorded EFM signal; FIG. 2B illustrates the schematic diagram when the decoder treats the overlapped region as two frames; and FIG. 2C illustrates the schematic diagram when the decoder treats the overlapped region as one frame. As shown in FIG. 2A, if the (n+2)-th frame and the (n+1)-th frame are overlapped, optical disk reading errors will occur because the (n+1)-th frame is covered by the (n+2)-th frame, and the (n+1)-th frame and the (n+2)-th frame cannot be correctly recognized. For example, if the signal is treated as two frames as in FIG. 2B or as one frame as in FIG. 2C, data errors occur.
Next, FIG. 3A illustrates the situation when a gap exists between two recorded frames. Three signals are shown: the signal before the recording being interrupted, the signal after the recording being succeeded, and the recorded EFM signal; FIG. 3B illustrates the situation that the decoder treats the overlapped region as two frames; and FIG. 3C illustrates the situation that the decoder treats the overlapped region as one frame. As shown in FIG. 3, if the (n+1)-th frame (being succeeded recording) and the n-th frame (being interrupted) are spaced apart by a linking gap, read errors may occur because the linking gap has no sync pattern and the optical disk cannot correctly recognize the frames during the reading procedure. For example, if the signal is treated as two frames as in FIG. 2B or as one frame as in FIG. 2C, data errors occur. Consequently, it is important to position the recording interruption position correctly to succeed the recording.